1. Field of The Invention
The present invention relates generally to a flywheel for a power transmission system which transmits driving force from an engine or the like. More specifically, the invention relates to a flywheel which can damp a torsional vibration transmitted thereto.
2. Description of The Background Art
In recent years, various attempts have been made to decrease vibrations and noises in a vehicular body by decreasing vibrations in a power transmission system. For example, Japanese Patent First (unexamined) Publication (Tokkai Sho.) No. 59-131043 discloses a flywheel which can damp or attenuate torsional vibrations of a drive shaft. This flywheel comprises an input member fixed to a drive shaft, an output member engaging the input member so as to be rotatable relative thereto, and a fluid clutch for connecting the input and output members to each other. When torsional vibrations are caused on the drive shaft due to variations of engine torque, this flywheel is designed to produce a fluid viscous resistance in the fluid clutch to damp or attenuate the torsional vibrations of the drive shaft while it transmits the engine torque from the input member to the output member.
In the case of this flywheel, the fluid clutch comprises a plurality of discs, each of which is rotatable relative to the adjoining disc, so that the fluid viscous resistances caused by the relative rotations of the discs damp torsional vibrations of the drive shaft. However, in such a flywheel, it is difficult to make dimensions between the adjoining discs accurate, that is; it tends to produce dispersion in distances between the adjoining discs. For that reason, there is a disadvantage in that great dispersion in viscous resistance value (i.e., a torsional vibration damping force) tends to occur between one and another of the products when manufactured.